Résumé:
In this thesis, we address the issue of time delays that commonly appear in ordinary differen
tial equations (ODEs).
The purpose of this thesis is to explore the types of problems that cannot be solved by ODEs
and require delay differential equations (DDEs) for their solution. We will also study some
of the key results of DDEs that correspond to their counterparts in ODEs, with a particular
focus on DDEs with constant delay.
Additionally, we will discuss the concept of stability in delayed differential equations DDEs.